1. Field of the Invention
The present invention relates to an optically active diphosphine having a bicyclo[2.2.1]heptane skeleton, an optically active intermediate for the production thereof and processes for producing these compounds.
2. Description of the Related Art
In syntheses of many organic compounds having an asymmetric carbon such as used for medicines, agricultural chemicals and the like, asymmetric syntheses which produce useful enantiomers only and the production or unnecessary use of less pharmacologically active medicines, thus, saving resources and protecting environment and ecosystem, have been in high demand.
Heretofore, asymmetric hydrolysis using microorganisms or enzymes and asymmetric esterification has been used as a technique of asymmetric synthesis.
However, catalytic asymmetric syntheses capable of producing a large amount of optically active compounds from a small amount of chiral source are recently most attractive.
As the important chiral source, there are used optically active metal complexes.
There are known various means for bringing metal complexes to an optically active environment.
An example of such means is to use optically active diphosphine ligands represented by (S)- or (R)-2,2'-bis (diphenylphosphino)-1,1'-binaphthyl (abbreviated as "(S)- or (R)-BINAP").
In particular, phosphines can stably coordinate to various metals, and can be widely used as effective ligands in many homogeneous metal catalytic reactions.
There are many known homogeneous catalytic asymmetric reactions using an optically active phosphine as an effective ligand, for example, synthesis of optically active amino acids by an asymmetric hydrogenation reaction of dehydroamino acid; synthesis of 1-menthol through an asymmetric isomerization reaction; and preparation of monomers for biodecomposition high polymers by an asymmetric hydrogenation of acetoacetic acid esters.
In catalytic asymmetric reactions, there is required a special catalytic property, that is, enantio-selectivity as well as ordinary catalytic properties such as reaction activity, selectivity and the like.
In order to improve these properties, there has been recent active investigation, in particular, in the development of optically active diphosphines having the capability of bidentate coordination.
There has never been synthesis of stereochemically controlled optically active diphosphines (such as those in the present invention) having the capability of bidentate coordination.
Syntheses of racemic modifications of such diphosphines are described only in C. P. Casey et al: J. Org. Chem., 55, 1394-96 (1990) and the present inventors: SYNLETT, 711-712 (1990).
In each of these processes for the preparation of the racemic modification, there is not an appropriate compound or method suitable for optical resolution in mid course of the preparation, and in addition, the resulting racemic modification itself can not be easily optically resolved.
Indeed, the above-mentioned methods are useful for producing the racemic modification, but the methods are not suitable for the production of optically active compounds which are the subject matter of the present invention.